The invention relates to a rolling mill for forming ribs on pipe. The ribbed pipes are used for heat exchangers in many applications.
The known rolling mills for forming ribbed pipes are equipped with a mill stand as a basic working unit. This mill housing is usually provided with three seats symetrically positioned relative to a vertical axis and fitted with hydraulic actuators with yokes, in which are rotatably mounted rolling tools. The tools in the form of packs of shaped discs mounted on common shafts, are driven by a common motor through shafts with Cardan joints. The tools are compressed from three sides against the pipe by hydraulic actuators, and this pressure together with rotation of said tools causes plastic strains in the pipe thus forming ribs.
Geometric parameters of rolling are controlled by adequate setting of the actuators in relation to the housing. And so, by shifting the actuator perpendicularly to the rolling axis, most often with a screw gear, a distance of the tool from a pipe being rolled is changed, and thereby the depth of ribs. By shifting hydraulically the tool from the pipe periodic ribbing of a predetermined pitch is obtained. To secure a particular fin pitch, the axes of the tools are set at a suitable angle relative to the rolling axis, the proper operation of the rolling mill being dependent on setting this angle uniformly for all the tools.
Most often, this is performed individually for each of the seats by turning a piston or cylinder of the actuator.
A rolling mill, referred to in Polish Patent Applications No. P-166964, is provided with tools attached directly to a movable piston, with which an angle of torsion of roller axes is set up in relation to rolling axis, and at the same time, the piston reciprocates to perform periodic rolling the ribs on a pipe.
Another example is a rolling mill referred to in Polish Patent application No. P-178698, wherein the tools are fixed directly to a movable cylinder, whose to-and-fro motion assures periodic rolling the ribs on a pipe, and an angle of torsion of axes of rollers relative to the rolling axis is accomplished simultaneously for three cylinders by intermediate means engaged with said cylinders.
The so designed rolling mills to form cross ribbed pipes do not result in easy and accurate fixing the tools and adjustment of performance parameters for a rolling mill. Assembly and current control of satisfactory operation of the attachment are difficult due to a complicated design of the whole mill stand. Equally complicated are devices shown in USSR Pat. No. 493,285 as well as U.S. Pat. Nos. 2,730,158 and 3,389,589, and German Published Application No. 2,037,839.